#coding:utf-8
score = int (input("请输入一个分数:"))
if 100 >= score >=90:
    print ('A')
elif 90 >= score >=80:
    print ('B')
elif 80 >= score >= 60:
    print('C')
elif 60 >= score >= 0:
    print('D')
else:
    print ('输入错误！')

